The majority of patients undergoing cataract removal receive an intraocular lens which does not provide for both near and distance vision. These patients then usually require some form of refractive correction, such as spectacles or contact lenses to achieve both near (reading) and distance (driving) vision. There is thus a need for intraocular lenses that will enable cataract surgery patients to perform activities requiring near and distance vision, especially in extreme lighting conditions, without spectacles.
Concentric bifocal intraocular lenses are known. U.S. Pat. No. 4,636,211, issued to Nielsen et al., discloses an intraocular lens with concentrically oriented near vision and far vision zones, with the near vision portion centrally positioned and the far vision portion coaxial with and surrounding the near vision portion. U.S. Pat. No. 4,813,955, issued to Achatz et al., discloses a multifocal intraocular lens whose optic portion is divided into near and far range zones such that the rays received by the pupil of the eye pass through near and far range zones of approximately equal areas.
Although prior, concentric, bifocal lenses have optics with portions which will provide for near and distance vision, there can be problems upon implantation due to, among other things, fluctuations in pupil size and spherical aberration phenomenon resulting in non-coincident images from different zones in a lens intended for the same distance correction.
The intraocular lenses of the present invention overcome the aforementioned problems through the use of a three zoned refractive optic for the provision of near and distance vision over the entire human pupil range, especially in extreme lighting conditions, with the peripheral distance zone corrected for spherical aberration such that rays of light passing through the central and peripheral zones form a coincident image in aqueous.